Point-to-Point Layout Review

[Thisismyname]

For my 6th build, I'm doing what I've wanted to do for a long time; build from a blank chassis with point-to-point wiring for shorter wire runs and localized filtering, optimized noise-reduction techniques etc

I'm building a Tweedle Dee Deluxe with an additional NFB switch. Here is my to-scale layout.
If anyone has the time, I'd appreciate a review, mostly to see if there are errors in regards to noise reduction, but also if there are any other things I may have overlooked.

 The layout has a key for easy navigation. The black line on the top and bottom of the bottom plane is how far the pot tabs and jacks will stick out once they are mounted, so any wire runs that go past that line won't exist.

Thanks for any and all help.

[SILVERGUN]

I breezed over the layout and saw 2 items to fix. I didn't have anymore time and there must be more, but the first would be that the shared output tube 25uf bypass cap is placed backwards and then there is this dead short:

[CascoSieg]

I think your cathode bypass cap on V3/V4 is backwards... (-) to ground, right?

[JPK]

I'd just arrange the 3 caps B+ 2,3,4 next to each other in a row. Use only one long term strip for + side (or mount two together to make a longer one). Would look cleaner. But I recon P2P is not too look cleaner but have the shortest leads/wires.


I'd go from the cord set to the fuse first --> switch --> PT.

[Thisismyname]

I breezed over the layout and saw 2 items to fix. I didn't have anymore time and there must be more, but the first would be that the shared output tube 25uf bypass cap is placed backwards and then there is this dead short:

Thanks for your input.

Regarding the short, I think that happened when I switched the t-strips from center mount to outer mount and I forget to fix it.

Regarding the output tube cap, I'm surprised I missed that. I would have done it right on the actual build, but as a good practice, I should be as serious about the digital layout as I am with the build.

Thanks

[Thisismyname]

I'd just arrange the 3 caps B+ 2,3,4 next to each other in a row. Use only one long term strip for + side (or mount two together to make a longer one). Would look cleaner. But I recon P2P is not too look cleaner but have the shortest leads/wires.


I'd go from the cord set to the fuse first --> switch --> PT.

Ya, I'll try that and see how I like it. It does seem needlessly messy.

Thanks

[NewYorker]

That series of 3M and 3x 10M resistors above V2 will sum to 33M, when what you need is 3.3M.

Ed

[Thisismyname]

That series of 3M and 3x 10M resistors above V2 will sum to 33M, when what you need is 3.3M.

Ed

I got the schematic off if Rob Robinette's site, and he wrote a note saying it's a typo and should be 33M. That's my only reference though.

[sluckey]

That series of 3M and 3x 10M resistors above V2 will sum to 33M, when what you need is 3.3M.

Ed

I got the schematic off if Rob Robinette's site, and he wrote a note saying it's a typo and should be 33M. That's my only reference though.

Here's one more reference. This is a pic of the real deal by Dumble. It clearly shows a 3.3M.

[bmccowan]

Interesting project. I built a 5C/E circuit with 6SL7 preamp tubes many years ago and often think of incorporating the Tweedle Dum mods.
I'm not being snarky or suggesting you change your mission, but when I opened the layout it was not what I expected to see. To me, point-to-point does not use all those tag strips. It is laid out tube socket to socket; sockets to ground; uses extra socket lugs as convenience solder lugs; etc.
Most old PA amps and many old guitar amps were done that way. Its harder to do these days because modern component leads are wimpy compared to the old caps and resistors. I like using tag strips, but I do not see any noise advantage compared with well done turret boards. Careful routing of wires (you are doing that) and using the best resistors, such as Dale mil-spec should help on noise. And once its running, swapping in tubes to find quiet ones.
Anyways maybe the point-to-point thing is just semantics - after all, who gets to decide these things. Best of luck with the project, I'll be curious as to how it works out.

[sluckey]

This discussion is the origin of all the Tweedle Dee information...

     http://ampgarage.com/forum/viewtopic.php?t=25054

[Thisismyname]

Interesting project. I built a 5C/E circuit with 6SL7 preamp tubes many years ago and often think of incorporating the Tweedle Dum mods.
I'm not being snarky or suggesting you change your mission, but when I opened the layout it was not what I expected to see. To me, point-to-point does not use all those tag strips. It is laid out tube socket to socket; sockets to ground; uses extra socket lugs as convenience solder lugs; etc.
Most old PA amps and many old guitar amps were done that way. Its harder to do these days because modern component leads are wimpy compared to the old caps and resistors. I like using tag strips, but I do not see any noise advantage compared with well done turret boards. Careful routing of wires (you are doing that) and using the best resistors, such as Dale mil-spec should help on noise. And once its running, swapping in tubes to find quiet ones.
Anyways maybe the point-to-point thing is just semantics - after all, who gets to decide these things. Best of luck with the project, I'll be curious as to how it works out.

Thanks for the input.

I should have mentioned it's more of a hybrid P2P layout. More 2-D than 3-D.
I'm pretty excited! The complete creative control is what I like. The other amps I've done have been eyelet and turret boards inside of pre-drilled chassis, so I've been "forced" to build around the pre-existing holes.
It's never been a problem, but I want to overbuild an amp just for the experience and to satisfy the perfectionist in me. Whatever the outcome, it'll still be fun.

I'll post updates as it comes into fruition.

[bmccowan]

I get it. I have done that a bunch myself. Working from a blank chassis, a Sharpie, drill bits, and chassis punches. I also have bought discontinued chassis for unknown amps and fit a circuit to them. That is fulfilling my Scottish (or maybe it is Scot-ish?) frugal ancestry.
I bet you will have a great sounding amp.

[SILVERGUN]

I should have mentioned it's more of a hybrid P2P layout. More 2-D than 3-D.
I'm pretty excited! The complete creative control is what I like. The other amps I've done have been eyelet and turret boards inside of pre-drilled chassis, so I've been "forced" to build around the pre-existing holes.

I really enjoy working like that. Here's one in it's final tweaking state.
It dawned on me that it would be pretty difficult to have to change out a bad preamp socket if that ever came to be.
Just posting for visual reference and in case there's any tidbits of interest.

[shooter]

for visual

very nice eye candy, you're movin on up 
the stubby gator n crack lighter are nice additions 

[Thisismyname]

I should have mentioned it's more of a hybrid P2P layout. More 2-D than 3-D.
I'm pretty excited! The complete creative control is what I like. The other amps I've done have been eyelet and turret boards inside of pre-drilled chassis, so I've been "forced" to build around the pre-existing holes.

I really enjoy working like that. Here's one in it's final tweaking state.
It dawned on me that it would be pretty difficult to have to change out a bad preamp socket if that ever came to be.
Just posting for visual reference and in case there's any tidbits of interest.

I really love looking at different layouts. I could do it for hours!
Thanks for the picture!

[NewYorker]

That series of 3M and 3x 10M resistors above V2 will sum to 33M, when what you need is 3.3M.

Ed

I got the schematic off if Rob Robinette's site, and he wrote a note saying it's a typo and should be 33M. That's my only reference though.

Here's one more reference. This is a pic of the real deal by Dumble. It clearly shows a 3.3M.

Yes, I just found Rob Robinette's note about the 3.3M / 33M typo.  However, his layout diagram shows 3.3M.

I assume that 33M would lessen the LNFB effect?

I suppose you could build it as you've laid (layed?) it out, and put a jumper across the 3 10M's to find out what 3M sounds like, compared to 33M.

FWIW,
Ed

[SILVERGUN]

crack lighter

How'dja guess?
Not everyone in Philly is.....

[Thisismyname]

I really enjoy working like that. Here's one in it's final tweaking state.
It dawned on me that it would be pretty difficult to have to change out a bad preamp socket if that ever came to be.
Just posting for visual reference and in case there's any tidbits of interest.

Cool build!
What is it?

Interesting winding for the OT primary. It reminds me of 3-phase power sine waves.

Do you have any tips for using t-strips?
I've only used 2 and wasn't thrilled by my solder joints. With turrets and eyelets, I can get mirror-like shines, but when I soldered the t-strips, it turned out a little cloudy and a lot of my solder just fell to the base of the tab. It worked fine, but wasn't very pretty.

Side note; Sorry for the flawed format, I'm still figuring out how to do certain things on this site.

[shooter]

working at the BBG, sadly, it's not just a big city problem.


your PS filter stages, do I count 6?

[SILVERGUN]

your PS filter stages, do I count 6?

Yup. This is when I thought over-filtering was the most valiant thing I could do to a PS.
1st stages are SS rect > cap > 180R > cap/plate supply > onward downstream

[SILVERGUN]

Cool build!
What is it?

Interesting winding for the OT primary. It reminds me of 3-phase power sine waves.

Do you have any tips for using t-strips?
I've only used 2 and wasn't thrilled by my solder joints. With turrets and eyelets, I can get mirror-like shines, but when I soldered the t-strips, it turned out a little cloudy and a lot of my solder just fell to the base of the tab. It worked fine, but wasn't very pretty.

Side note; Sorry for the flawed format, I'm still figuring out how to do certain things on this site.

This is an older build that is still not complete. SE EL34 with a 2nd stage EF86. It was the first time that "my design" did not sound like I intended. It was great that I had built it on terminal strips because I was able to make many, many mods without much concern for space or layout. It now has a reverb circuit built into the bottom left hand corner and it is close to good. I hope to get back to it during a snow-in, but that hasn't happened recently.
As far as terminal strips go, I treat them with a welding technique. Whenever you're welding dissimilar thicknesses of material you start the weld by putting the heat into the thicker material. Same approach with the TS. I use a HOT pencil with a flat section of tip. I put flux on the component and wrap and crimp tight on the terminal for a positive mechanical connection. I almost always use a heatsink on the component. I heat the terminal first by trying to get the flat side of the soldering tip flat against the terminal. 3-4 seconds holding on the terminal and then I lean the tip onto the component lead and immediately add solder and then immediately remove the heat. It is a "feel thing". I never try to fill the hole in the terminal or worry about looks. I almost always use the Keystone brand terminal strips and make sure they are clean to start. And, as sluckey will remind you, clean your tip after EVERY use.
Hope that helps.
I have also held the amp upside down with the tip on the terminal to get the solder to flow back where i want it. Gravity works.

[bmccowan]

Silvergun - that seems like great advice on soldering t strips. Some of it I do, the rest I will try. I will add that I think some of the reasons that turrets are easier to solder to, is that the good ones, like those on Doug's boards are well plated. And its easier to make a solid mechanical connection. And with turrets its easy to heat one side of the turret with a hot iron (700+) bring in the solder on the other side and when it flows around the turret you are done.
Tag strip quality varies a lot and some need to be fluxed and pre-tinned to take solder well - I'm not sure what brands I have been buying - most have come from AES. I clean the iron tip and tin it after every use. They last a lot longer than when I slacked on that.

[Thisismyname]

Thanks for the great info! I'm sure it won't take me long to get down.